1. Field of the Invention
The present invention relates to a scroll-type compressor.
2. Description of Related Art
A scroll-type compressor includes a first scroll member and a second scroll member within a housing. The first scroll member is provided as a fixed scroll member. The second scroll member is provided as an orbital scroll member for nonrotatable, orbital movement relative to the first scroll member. The rotation of the second scroll member is prevented by rotation preventing mechanism provided in the compressor. The first scroll member has a first end plate and a first spiral element which axially extends from the first end plate. The second scroll member has a second end plate and a second spiral element which axially extends from the second end plate. The first spiral element and the second spiral element interfit at an angular and radial offset to make a plurality of line contacts which define at least one pair of sealed off fluid pockets. The sealed off fluid pockets move radially inwards due to the nonrotatable, orbital movement of the second scroll member, and decrease in volume, thereby, compressing the fluid.
A ball coupling-type mechanism may be used as the rotation preventing mechanism for the second scroll member. In a usual ball coupling-type rotation preventing mechanism, a ring for regulating balls and thrust plates for receiving balls are made separately. In a rotation preventing mechanism having such a structure, a shim generally is used for adjusting an axial gap between the first and second scroll members. In this structure, by selecting an appropriate thickness of the shim, the compressor may be assembled, so that a preload is not generated in the rotation preventing mechanism and between the first and second scroll members within a range that does not affect the performance of the compressor.
A scroll-type compressor has been proposed that uses a rotation preventing mechanism, wherein the ring for regulating balls and the thrust plates for receiving balls are made integrally. Such a ball coupling has a pair of rolling ball regulating plates, each integrally formed as a ring-like plate, and a plurality of balls interposed between the rolling ball regulating plates. The ball coupling is disposed between the second scroll member and a fixed portion of the compressor, such as a front housing facing the second scroll member, so that the pair of rolling ball regulating plates axially face each other. Each rolling ball regulating plate has a plurality of ball rolling grooves that are disposed in the circumferential direction about the plate. Each ball rolling groove may be formed as a ring-like groove. Each ball is disposed between the respective ball rolling grooves of the respective plates, and rolls along the ball rolling grooves during the operation of the compressor for allowing the nonrotatable, orbital movement of the second scroll member. Such a ball coupling has a small number of parts.
However, the rolling ball regulating plate of such a ball coupling generally has a problem that a deformation, such as a distortion or a torsion, is easily generated. For example, a torsion of a single rolling ball regulating plate itself, or a distortion occurring when the ball coupling is assembled, may be generated. In such a condition, it is difficult to properly adjust an axial gap between the first and second scroll members to achieve a desired performance of the compressor. Further, because it is difficult to place the balls at proper positions in the respective ball rolling grooves, the behavior of the balls is unstable. Subsequently unstable behavior of the balls will induce chipping of the plate or generation of noise.